Biomechanical Evaluation of Additional Surgical Maneuvers to Improve Symmetry in Performing Nuss Procedure for Asymmetric Pectus Excavatum.

Background: Severing part of the thorax prior to bar placement is effective to improve outcomes in performing the Nuss procedure for asymmetric pectus excavatum. This study aims to elucidate the patterns of severing to provide an ideal outcome. Methods: Three-dimensional biomechanical computer models were produced simulating the thoraxes of 10 actual patients with asymmetric pectus excavatum. Virtual surgical operation was performed on the 10 models in 4 patterns: group 1-no part of the thorax was severed (default group). Group 2-The sternum was severed (sternum-severing group). Group 3-The ribs on the affected side were severed (rib-severing group). Group 4-Both the sternum and ribs on the affected side were severed (sternum/rib-severing group). After performing this preparation, simulation of bar placement was performed. Comparing the pre- and postoperative shapes of the models, we examined whether symmetry improved for each group. Results: Symmetry of the chest wall improved for rib-severing group and sternum/rib-severing group. Asymmetry remained for default group and sternum-severing group. Conclusions: Performance of the Nuss procedure for asymmetric pectus excavatum does not greatly improve symmetry of the chest wall. Severing the ribs as an additional maneuver is effective to improve symmetry.